Appliance for disinfection of HVAC systems

ABSTRACT

A device ( 20 ) for Disinfection of HVAC Systems that include features that will protect service personnel from un-intended exposure to ultra violet radiation. The safeguards include an interlock ( 70 ) that prevents illumination of germicidal lamps ( 80 ) when an enclosure within which the germicidal lamps ( 80 ) are mounted is not properly attached to a duct or appliance; the apparatus further provides for innovative methods for determining that the germicidal lamps ( 80 ) are operating.

FIELD OF THE INVENTION

This invention relates to an appliance for use in the disinfection ofheating ventilation and air conditioning systems (“HVAC”). Moreparticularly, this invention relates to a device for killingmicroorganisms in both an air stream and/or stationary components withinan HVAC system such as cooling coils, duct components and filter media,by irradiation with ultraviolet light (“UV”). The basic components ofthe system are an enclosure, removable UV lamp assemblies, a powersupply to supply electrical power to the lamps, and various mechanicaland electrical features to improve performance, convenience and safety.

More specifically, the present invention reduces the risk that thoseinvolved in installation and maintenance of HVAC equipment will beexposed to ultraviolet radiation when lamps are serviced or replaced, orwhen the unit is not properly positioned in a duct. Embodiments of theinvention may also provide an indication of lamp operation visible fromthe outside of the duct to eliminate any need for direct visualobservation of the lamps. An additional safety feature shuts off powerto the lamps that produce ultraviolet radiation whenever a serviceperson attempts to open the enclosure or remove the lamps to preventexposure to harmful UV radiation. Other features of the inventionprovide improved performance and also ease of maintenance.

The inventive appliance is located within a self-contained unit that isinstalled in a portion of the duct work of an HVAC system or within acentral HVAC appliance, such as a furnace, air conditioner orventilating unit. The unit is generally mounted through an opening inthe side of an HVAC duct. The electrical connections and ports arelocated on the outside of the duct, while the mercury vapor lamps thatproduce UV are located within the duct.

BACKGROUND OF THE INVENTION

Ultraviolet light in the range of wavelengths of from 180 to 300 nm hasbeen used for the disinfection of air, water and surfaces for manyyears. Wavelengths near 253.7 nm are particularly useful for killingbacteria, viruses, fungus, mold and spores, and are convenientlygenerated by low pressure mercury vapor lamp. Many devices and methodsfor utilizing UV for disinfection are dislcosed in the prior art.Included in the prior art are devices for use in HVAC equipment fortreatment of air streams and surfaces. However, these devices have notadequately addressed safety and performance issues.

“Disinfection” refers to killing pathogenic or otherwise undesireablemicro-organisms. Products using short-wave ultraviolet radiation withwavelengths in the range of 180 to 350 nm have been used to disinfectair streams in residential and commercial HVAC systems. This is a highenergy form of radiation that is not visible to humans. While this highenergy ultraviolet light is capable of destroying a variety ofbiological pathogens and non-pathogenic, but nevertheless undesirableorganisms, it is also hazardous to humans. Short wavelength ultravioletradiation has been determined to be the cause of skin cancers, such asmelanoma, and some cases of non-Hodgkins lymphoma by the National Centerfor Chronic Disease Prevention at the Centers for Disease Control andPrevention and by the National Cancer Institute. The eyes areparticularly susceptible to damage caused by ultraviolet radiation. Theupper threshold for exposure of the human eye to ultraviolet light hasbeen set at 3 millijoules per square centimeter.

The lamps typically used to produce ultraviolet radiation for germicidalapplication produce a flux of ultraviolet radiation well in excess ofthis threshold, often 100 to 1000 times higher. Therefore, protectivemeasures should be taken to protect workers and consumers who useultraviolet light for germicidal applications.

Protective eyewear can adequately protect workers from health risk whileworking with ultraviolet devices. However, examination of Worker'sCompensation Insurance claims reveal that one-half of the ultravioletradiation related eye injuries occurred to workers who were inpossession of, but neglected to use, proper protective eyewear.

In the past, sterilization and disinfection units were inadequatelyprotected. While some units have electrical or mechanical mechanismsthat may shut off a UV emitting germicidal lamp when it is removed fromits enclosure, the device may be energized prior to installation,thereby subjecting the user or service person installing the unit toultraviolet radiation.

Accordingly, an object of the invention to provide an appliance fordisinfection of HVAC systems wherein only lamps that are optimized forthe system can be mounted in the system;

It is a further object of the invention to provide an appliance fordisinfection of HVAC systems designed to allow assessment of germicidallamp performance without risk of exposure to ultraviolet radiation.

SUMMARY OF THE INVENTION

The present invention provides an integrated appliance for disinfectionof HVAC systems that overcomes the deficiencies of prior art devices byproviding a separate lamp assembly for each germicidal lamp. Theinvention may further provide that each lamp assembly can be separatelyremoved from the appliance, and may further provide an optical signalfor assessing performance of the lamp mounted in the lamp assembly. Theinvention may further provide novel switch assemblies that preventapplication of electrical power when an enclosure containing the lampsis open for servicing, thus preventing exposure of service personnel toultraviolet radiation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a front view of the device.

FIG. 1B is a side view of the device.

FIG. 2 is a cut-away side view.

FIG. 3 shows the lamp handler/retainer assembly.

FIG. 4A is a front view showing the device mounted in a duct.

FIG. 4B is a side view showing the device mounted in a duct.

FIG. 5 shows the switch of the device.

FIG. 6 is a circuit diagram for the device.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIG. 1, in one embodiment, the appliance comprises anenclosure case (10) and a base (20). Base (20) is mounted to a wall ofan HVAC duct (25). One or more openings are cut in the wall of the ductfor the germicidal lamps (30) to project into the interior of the duct.

Base (20) includes a mechanical mount for one or more germicidal lamps,the electrical connections to the lamps, a power supply and ballast. Thenumber of germicidal lamps (30) is determined by the intensity of theultraviolet radiation required for the particular application. Thegermicidal lamps may be of a commercial design or specially made forthis application. To insure the best match between lamp characteristicsand the electrical properties of the power supply and ballast, inpreferred embodiments germicidal lamps (30) are provided with speciallydesigned mounts to engage lamp mounts on base (20) as described ingreater detail below. The germicidal lamps may be configured as a singlelongitudinal tube (single or double ended), or a multi-axial tube.

The germicidal lamps are mounted in a specially designed socketdescribed in greater detail below. As shown in FIG. 2 each lamp socketincludes electrical connections to the lamp mounted therein. As alsoshown in FIG. 2 in preferred embodiments, lamp 65 socket is formedintegral with handle base 60 to form lamp assembly 75 which is installedwith the enclosure case 10. A section view of the lamp assembly is alsoshown in FIG. 2.

Each lamp is mounted separately in its own lamp assembly, allowing eachlamp to be separately removed from service. As shown in FIG. 3 and inmore detail in FIG. 5, the lamp assembly includes a handle base (60), ahandle cover (120), a connection circuit board 125 and an indicatorlight (130), which, as discussed in greater detail below, provides anoptical signal indicative of the state of operation of the lamp mountedon the particular lamp assembly. Lamp assembly 75 is attached to theenclosure case using a bayonet mount (not shown). A handle attached tothe lamp assembly is grasped and rotated to release the lamp assemblyfrom the enclosure case when it is necessary to service or replace thelamp. An end view of the enclosure case, with two lamp assembles isshown in FIG. 1A.

The invention further includes a duct mounting interlock (15) thatprevents electrical power from reaching the ultraviolet lamps unless theenclosure is installed on an HVAC duct. Electrical power for thegermicidal lamps is routed through a switch that is closed when a unitis attached to a duct or appliance. In preferred embodiments the switchis a paddle switch mounted on unit (20). When switch (15) is closed byattaching unit (20) to an HVAC duct or appliance, electrical current canreach the germicidal lamps.

In embodiments with provision for more than one lamp assembly in anenclosure, power will not be supplied to any lamp assemblies unless alllamp assemblies are installed. This aspect of the invention protectsservice personnel from exposure to UV radiation that would otherwiseescape from the enclosure through unused openings for lamp assemblies.The presence of lamp assemblies may be detected by, for example,mechanical switches located adjacent to bayonet mounts for the lampassemblies.

Another embodiment of a device that prevents power from reaching thegermicidal lamps unless the enclosure is installed in an HVAC duct orappliance is depicted in FIGS. 4 and 5. A side sectional view of thisembodiment is shown in FIG. 4. In this embodiment, mounts for UV lampsare installed in a narrow box-shaped housing 160. In this embodiment,two conditions must be met before power is applied to the germicidallamps. First, housing (160) must be mounted on the wall of a duct (170).Second, cover (180) must be attached to cover (180). Under theseconditions, UV light will not be emitted unless the appliance of thepresent invention is attached to an HVAC duct, on one side, and that acover is attached to the opposite side. Thus UV light should not be ableto escape from the appliance.

Switch bracket (190) is mounted on a portion of the wall of housing(200) that is made flexible by cutouts made in wall forming a “v” shapedleaf spring (210). When housing (160, in FIG. 4) is mounted on duct wall(170) bracket tab (190) is deflected inward against spring pressureproduced by leaf spring (220). As a consequence, switch bracket (190),which is attached to bracket tab (190) moves inward as well.

Interlock switch (230) is fixed to the end of switch bracket oppositethe point at which switch bracket (190) is attached to leaf spring(210). Thus when switch bracket (190) is deflected inward, interlockswitch (230) is carried forward as well. When interlock switch contactscover screw (240) which is used to secure cover (250) in place,interlock switch (230) is defected backward, thus closing an electricalcircuit that supplies power to germicidal lamps within the appliance.Thus, unless the appliance is mounted on an HVAC duct, pressing brackettab (220) inward, and cover is attached to housing (160), power will notbe applied to the germicidal lamps, and no UV will be produced. Thismechanism will help to prevent inadvertent exposure to UV radiationproduced by those who service and maintain the appliance.

An additional safety feature of the invention is a visible indicator asto whether each lamp installed in a appliance according to the inventionis illuminated. As shown in FIG. 6, AC power is supplied to thefilaments of a low pressure mercury vapor germicidal lamp (260) througha pair of power circuits (270). Two pair of oppositely oriented diodes(275) are interposed in an arm of one power circuit (270). A lightemitting diode (“LED”) (280) illuminates when a voltage drop is presentacross the diode pair. The LED is only illuminated for a half cycle ofthe power wave form, but at frequencies of 60 Hz used in mostinstallations, the off time is not detectable. Lamp failure is thereforereadily detected, as the LED is not illuminated when there is no currentflowing through the diodes.

The lamp base of the present invention is specifically implemented toprevent the installation of germicidal lamps not intended for use withthe present invention. Although there are many sources for germicidallamps, it is preferable to use lamps optimized for use with theinventive appliance disclosed and claimed herein. In some cases, lampsnot designed for use with the present invention may not deliver theenergy required by the particular installation.

Prior art appliances were designed to retain germicidal lamps in avariety of inefficient and costly designs. Some lamps were affixed to abase with a synthetic potting material. Others have used an awkwardretaining device that may not prevent the installation of incorrectlamps. Other solutions provide a means to mount the germicidal lampwithin the device, but are costly or difficult to manufacture. As shownin FIG. 2, the present invention employs a lamp base that engagesprotrusions formed on the lamp base with one-way barbs (110). Thisengagement mechanism securely fastens the germicidal lamp to the lampbase.

The foregoing description of the embodiments of the invention isprovided for illustrative purposes and should not be understood to limitor otherwise to define the scope of the invention, which is provided bythe claims appended hereinbelow.

1. An apparatus for preventing operation of at least one germicidal lampin an HVAC system under unsafe conditions comprising: a housing; a firstswitch on a side of the housing used to access the at least onegermicidal lamp for servicing; a second switch on a side of the housingthat is in contact with an HVAC duct or appliance, wherein power issupplied to the at least one germicidal lamp only when the first andsecond switches are in a condition indicating that the UV light cannotbe emitted through the housing.
 2. The apparatus of claim 1, wherein thefirst switch is a leaf switch.